feat: add in memory implementation of HeightIndex Database

database/database.go

@@ -95,17 +95,29 @@ type Database interface {
 	health.Checker
 }
 
-// HeightIndex defines the interface for storing and retrieving entries by height.
+// HeightIndex defines the interface for storing and retrieving values by height.
 type HeightIndex interface {
-	// Put inserts the entry into the store at the given height.
-	Put(height uint64, bytes []byte) error
+	// Put inserts the value into the database at the given height.
+	//
+	// A nil or empty slice for [value] is allowed and will be returned as nil
+	// when retrieved via Get.
+	//
+	// Note: [value] is safe to read and modify after calling Put.
+	Put(height uint64, value []byte) error
 
-	// Get retrieves an entry by its height.
+	// Get retrieves a value by its height.
+	// Returns ErrNotFound if the key is not present in the database.
+	//
+	// Note: Get always returns a new copy of the data.
 	Get(height uint64) ([]byte, error)
 
-	// Has checks if an entry exists at the given height.
+	// Has checks if a value exists at the given height.
+	//
+	// Return true even if the stored value is nil, or empty.
 	Has(height uint64) (bool, error)
 
 	// Close closes the database.
+	//
+	// Note: Calling Close after Close returns ErrClosed.
 	io.Closer
 }

database/heightindexdb/dbtest/dbtest.go

@@ -0,0 +1,250 @@
+// Copyright (C) 2019-2025, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package dbtest
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ava-labs/avalanchego/database"
+)
+
+// Tests is a list of all database tests
+var Tests = map[string]func(t *testing.T, newDB func() database.HeightIndex){
+	"PutGet":              TestPutGet,
+	"Has":                 TestHas,
+	"CloseAndPut":         TestCloseAndPut,
+	"CloseAndGet":         TestCloseAndGet,
+	"CloseAndHas":         TestCloseAndHas,
+	"Close":               TestClose,
+	"ModifyValueAfterPut": TestModifyValueAfterPut,
+	"ModifyValueAfterGet": TestModifyValueAfterGet,
+}
+
+type putArgs struct {
+	height uint64
+	data   []byte
+}
+
+func TestPutGet(t *testing.T, newDB func() database.HeightIndex) {
+	tests := []struct {
+		name        string
+		puts        []putArgs
+		queryHeight uint64
+		expected    []byte
+		expectedErr error
+	}{
+		{
+			name: "normal operation",
+			puts: []putArgs{
+				{1, []byte("test data 1")},
+			},
+			queryHeight: 1,
+			expected:    []byte("test data 1"),
+		},
+		{
+			name: "not found error when getting on non-existing height",
+			puts: []putArgs{
+				{1, []byte("test data")},
+			},
+			queryHeight: 2,
+			expected:    nil,
+			expectedErr: database.ErrNotFound,
+		},
+		{
+			name: "overwriting data on same height",
+			puts: []putArgs{
+				{1, []byte("original data")},
+				{1, []byte("overwritten data")},
+			},
+			queryHeight: 1,
+			expected:    []byte("overwritten data"),
+		},
+		{
+			name: "put and get nil data",
+			puts: []putArgs{
+				{1, nil},
+			},
+			queryHeight: 1,
+			expected:    nil,
+		},
+		{
+			name: "put and get empty data",
+			puts: []putArgs{
+				{1, []byte{}},
+			},
+			queryHeight: 1,
+			expected:    nil,
+		},
+		{
+			name: "put and get large data",
+			puts: []putArgs{
+				{1, make([]byte, 1000)},
+			},
+			queryHeight: 1,
+			expected:    make([]byte, 1000),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			db := newDB()
+			defer db.Close()
+
+			// Perform all puts
+			for _, write := range tt.puts {
+				require.NoError(t, db.Put(write.height, write.data))
+			}
+
+			// Query the specific height
+			retrievedData, err := db.Get(tt.queryHeight)
+			if tt.expectedErr != nil {
+				require.Equal(t, tt.expectedErr, err)
+			} else {
+				require.NoError(t, err)
+				require.Equal(t, tt.expected, retrievedData)
+			}
+		})
+	}
+}
+
+func TestHas(t *testing.T, newDB func() database.HeightIndex) {
+	tests := []struct {
+		name        string
+		puts        []putArgs
+		queryHeight uint64
+		expected    bool
+	}{
+		{
+			name:        "non-existent item",
+			puts:        []putArgs{},
+			queryHeight: 1,
+			expected:    false,
+		},
+		{
+			name:        "existing item with data",
+			puts:        []putArgs{{1, []byte("test data")}},
+			queryHeight: 1,
+			expected:    true,
+		},
+		{
+			name:        "existing item with nil data",
+			puts:        []putArgs{{1, nil}},
+			queryHeight: 1,
+			expected:    true,
+		},
+		{
+			name:        "existing item with empty bytes",
+			puts:        []putArgs{{1, []byte{}}},
+			queryHeight: 1,
+			expected:    true,
+		},
+		{
+			name: "has returns true on overridden height",
+			puts: []putArgs{
+				{1, []byte("original data")},
+				{1, []byte("overridden data")},
+			},
+			queryHeight: 1,
+			expected:    true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			db := newDB()
+			defer db.Close()
+
+			// Perform all puts
+			for _, write := range tt.puts {
+				require.NoError(t, db.Put(write.height, write.data))
+			}
+
+			exists, err := db.Has(tt.queryHeight)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, exists)
+		})
+	}
+}
+
+func TestCloseAndPut(t *testing.T, newDB func() database.HeightIndex) {
+	db := newDB()
+	require.NoError(t, db.Close())
+
+	// Try to put after close - should return error
+	err := db.Put(1, []byte("test"))
+	require.ErrorIs(t, err, database.ErrClosed)
+}
+
+func TestCloseAndGet(t *testing.T, newDB func() database.HeightIndex) {
+	db := newDB()
+	require.NoError(t, db.Close())
+
+	// Try to get after close - should return error
+	_, err := db.Get(1)
+	require.ErrorIs(t, err, database.ErrClosed)
+}
+
+func TestCloseAndHas(t *testing.T, newDB func() database.HeightIndex) {
+	db := newDB()
+	require.NoError(t, db.Close())
+
+	// Try to has after close - should return error
+	_, err := db.Has(1)
+	require.ErrorIs(t, err, database.ErrClosed)
+}
+
+func TestModifyValueAfterPut(t *testing.T, newDB func() database.HeightIndex) {
+	db := newDB()
+	defer db.Close()
+
+	originalData := []byte("original data")
+	modifiedData := []byte("modified data")
+
+	// Put original data
+	require.NoError(t, db.Put(1, originalData))
+
+	// Modify the original data slice
+	copy(originalData, modifiedData)
+
+	// Get the data back - should still be the original data, not the modified slice
+	retrievedData, err := db.Get(1)
+	require.NoError(t, err)
+	require.Equal(t, []byte("original data"), retrievedData)
+	require.NotEqual(t, modifiedData, retrievedData)
+}
+
+func TestModifyValueAfterGet(t *testing.T, newDB func() database.HeightIndex) {
+	db := newDB()
+	defer db.Close()
+
+	originalData := []byte("original data")
+
+	// Put original data
+	require.NoError(t, db.Put(1, originalData))
+
+	// Get the data
+	retrievedData, err := db.Get(1)
+	require.NoError(t, err)
+	require.Equal(t, originalData, retrievedData)
+
+	// Modify the retrieved data
+	copy(retrievedData, []byte("modified data"))
+
+	// Get the data again - should still be the original data
+	retrievedData2, err := db.Get(1)
+	require.NoError(t, err)
+	require.Equal(t, originalData, retrievedData2)
+	require.NotEqual(t, retrievedData, retrievedData2)
+}
+
+func TestClose(t *testing.T, newDB func() database.HeightIndex) {
+	db := newDB()
+	require.NoError(t, db.Close())
+
+	// Second close should return error
+	err := db.Close()
+	require.ErrorIs(t, err, database.ErrClosed)
+}

database/heightindexdb/memdb/database.go

@@ -0,0 +1,98 @@
+// Copyright (C) 2019-2025, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package memdb
+
+import (
+	"slices"
+	"sync"
+
+	"github.com/ava-labs/avalanchego/database"
+)
+
+var _ database.HeightIndex = (*Database)(nil)
+
+// Database is an in-memory implementation of database.HeightIndex
+type Database struct {
+	mu     sync.RWMutex
+	data   map[uint64][]byte
+	closed bool
+}
+
+func New() *Database {
+	return &Database{
+		data: make(map[uint64][]byte),
+	}
+}
+
+// Put stores data in memory at the given height
+func (db *Database) Put(height uint64, data []byte) error {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	if db.closed {
+		return database.ErrClosed
+	}
+
+	if db.data == nil {
+		db.data = make(map[uint64][]byte)
+	}
+
+	if len(data) == 0 {
+		// don't save empty slice if data is nil or empty
+		db.data[height] = nil
+	} else {
+		db.data[height] = slices.Clone(data)
+	}
+
+	return nil
+}
+
+// Get retrieves data at the given height
+func (db *Database) Get(height uint64) ([]byte, error) {
+	db.mu.RLock()
+	defer db.mu.RUnlock()
+
+	if db.closed {
+		return nil, database.ErrClosed
+	}
+
+	data, ok := db.data[height]
+	if !ok {
+		return nil, database.ErrNotFound
+	}
+
+	// don't return empty slice if data is nil or empty
+	if data == nil {
+		return nil, nil
+	}
+
+	return slices.Clone(data), nil
+}
+
+// Has checks if data exists at the given height
+func (db *Database) Has(height uint64) (bool, error) {
+	db.mu.RLock()
+	defer db.mu.RUnlock()
+
+	if db.closed {
+		return false, database.ErrClosed
+	}
+
+	_, ok := db.data[height]
+	return ok, nil
+}
+
+// Close closes the in-memory database
+func (db *Database) Close() error {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	if db.closed {
+		return database.ErrClosed
+	}
+
+	db.closed = true
+	db.data = nil
+	return nil
+}